For continued Secret clearance eligibility, the required periodic reinvestigation is Tier 3R.

Direct answer

  • The formal answer to the question “which periodic reinvestigation is required for continued secret clearance eligibility” is Tier 3R (Tier 3 Reinvestigation).
  • This label comes from the DoD personnel vetting/clearance training materials, where Secret-level access is associated with Tier 3 investigations and Tier 3R for the periodic reinvestigation.

Quick context

  • Secret clearances are tied to Tier 3 investigations in the current national security vetting structure.
  • When it is time to revalidate that you still meet eligibility standards, the periodic update is designated Tier 3R rather than Tier 5R or any other tier.

Why this matters

  • Training and exam-style questions about security clearances often test whether you can match each clearance level with the correct investigation tier and reinvestigation tier.
  • Remembering “Secret → Tier 3 → periodic reinvestigation Tier 3R” keeps the mapping clear and avoids confusing it with Top Secret, which is associated with Tier 5/Tier 5R.

TL;DR: For continued Secret clearance, the periodic reinvestigation required is Tier 3R.

Information gathered from public forums or data available on the internet and portrayed here.